Coriolis Effect

on the spinning Earth

Trajectoriesinertial reference frame

Trajectoriesrotating reference frame

Coriolis Force• Apparent force that deflects a path in the

rotating frame of reference

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Coriolis Force• Trajectory is straight; observer turns

beneath it

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Rotation of the Earth

• Rotates West to East(counterclockwise as seen from above North pole)

• Poles on axis; equator farthest from axis

Source: Earth and Moon Viewer,Copyright © 1989 by Jef Poskanzer.

Coriolis Force on EarthEarth rotates to the East

Source: Strahler and Strahler, Introducing Physical Geography, 2005.

Trajectories deflect right in N hemisphere

Coriolis Force on EarthWhat happens in the Southern Hemisphere?

Source: Strahler and Strahler, Introducing Physical Geography, 2005.

Trajectories deflect left in S hemisphere

Coriolis Force on Earth

• The direction toilets and bathtubs drain on earth is not determined by the Coriolis force.

• They are to small and they drain too quickly for the Coriolis force to matter.

Global Circulation

• Equatorial air rises– Moisture precipitates

– Air travels poleward

– Diverted by Coriolis effect– Sinks, warms– Converges to equator

Global Circulation

• Polar air sinks– Diverted by Coriolis effect

– Warms from ground, rises

– Moisture precipitates– Returns to poles